Since photography using a silver halide has excellent photographic characteristics such as sensitivity and gradation control as compared with other types of photography such as electrophotography and a diazo process, it has been used most widely so far. In recent years, a technology enabling the simple and rapid obtainment of an image has been developed by changing a processing method for forming an image of light-sensitive material using a silver halide from the conventional wet processing with a developing solution and the like near the normal temperature to a heat development processing using no developing solution.
A heat-developable light-sensitive material is known in the photographic technical field. The heat-developable light-sensitive material and its process are mentioned, for example, in Shashinkogaku no Kiso (Basis of Photographic Engineering) (published by Corona Co., 1979), pp. 553 to 555; in Eizo Joho (Image Information) (published in April, 1978), p. 40; in Neblette's Handbook of Photography and Reprography, 7th Ed., Van Nostrand Reinhold Company, pp. 32 and 33; in U.S. Pat. Nos. 3,152,904, 3,301,678, 3,392,020 and 3,457,075, in British Patents 1,131,108 and 1,167,777; and in Research Disclosure, RD No. 17029 (June, 1978), pp. 9 to 15.
Many methods have been proposed for obtaining a color image by heat development. Relating to a method for forming a color image by coupling of an oxidant of the developing agent with a coupler, there have been proposed a reducing agent of p-phenylenediamines and a phenolic or active methylene coupler in U.S. Pat. No. 3,531,286, a p-aminophenol type reducing agent in U.S. Pat. No. 3,761,270, a sulfonamido phenol type reducing agent in Belgian Patent 802,519 and in Research Disclosure (Sept. 31, 1975), pp. 31 and 32, and a combination of a sulfonamido phenol type reducing agent with a 4-equivalent coupler in U.S. Pat. No. 4,021,240.
A method for forming a positive color image by a light-sensitive silver dye bleaching process is mentioned, for example, in Research Disclosure, RD No. 14433 (April, 1976), pp. 30 to 32, in Research Disclosure, RD No. 15227 (December, 1976), pp. 14 and 15, and in U.S. Pat. No. 4,235,957.
Further, a method for forming an image by heat development which utilizes a compound having a dye part and able to release a mobile dye corresponding or counter-corresponding to a reduction reaction of silver halide to silver at an elevated temperature is disclosed in European Patent Application Nos. 76,492A and 79,056A, and in Japanese Patent Application (OPI) Nos. 28928/83 and 26008/83 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application").
Such a heat-developable light-sensitive material is developed by applying heat, but there often arise problems that the development progresses too far and fog increases because the light-sensitive material once heated requires too much time for its temperature fall and, in the case where a dye formed or released in a light-sensitive element is transferred to an image receiving element, excessive development is caused by heating for the transfer, and the transferred image has increased fog. Further, it is difficult to heat a light-sensitive material to a high temperature uniformly and unevenness of heating temperatures is formed. Even if a light-sensitive material is heated uniformly, an unevenness of the amount of image formation accelerators such as water, a base, and the like existent in the light-sensitive material is formed. Therefore, the heat-developable light-sensitive material presents problems that the development and the transfer of dye progress unevenly for the above-mentioned causes, thereby forming an image lacking in uniformity and lowering the image quality.